Incremental Launching

Somerset Engineering has designed many incremental launch schemes for steel bridges. They vary in complexity from simple one or two spans to curved plate girders and cable-stayed steel boxes with spans up to 125m (410’). The method of horizontal moving can also vary from simple reeved blocks and rigging to a more sophisticated hydraulic jacking system, either pushing or pulling the superstructure over the piers.

We optimise the length of the temporary nose by using the strongest section of the permanent bridge to limit the stresses in girders under cantilever condition. We analyse the full step by step process of the launch to check stresses and deflection as the bridge is advanced. All clearances of moving parts are checked as well as critical web buckling stresses. If any part of the permanent bridge is needed to be changed to suit the launch we work with the fabricator to incorporate these details.

Incremental launching is well suited to the design/build process. The advantage is that we can work with the bridge designer to incorporate all the necessary revisions in the details and member sizes to accurately price these changes into the job at bid stage. Once the job has been successfully awarded these details can be quickly finalised to incorporate into the shop drawings with minimum delay.